Measuring amps.

[Chegs]

I've just been reading up on mosfets as was convinced the Raptor was THE device I needed to create a variable power box mod, only now it seems that if I simply added a variable resistance to the mosfet this will vary the output on the atty.

Sent by lazer from just north of the world's largest nuclear dustbin

 

[RicModMaker]

I've just been reading up on mosfets as was convinced the Raptor was THE device I needed to create a variable power box mod, only now it seems that if I simply added a variable resistance to the mosfet this will vary the output on the atty.

Sent by lazer from just north of the world's largest nuclear dustbin

How do you do that? I've got a couple of vv boards I was going to use but if there's an easier way, I'm well up for it. Ideally, I'd like a nice twisty knob controller.

 

[doobedoobedo]

I've just been reading up on mosfets as was convinced the Raptor was THE device I needed to create a variable power box mod, only now it seems that if I simply added a variable resistance to the mosfet this will vary the output on the atty.

Sent by lazer from just north of the world's largest nuclear dustbin

This is true, however it's not that simple. You'd be creating a linear regulator which would burn off the excess power. It would get almost as hot as the coil. The raptor and all other regulators are switching regulators which are much more efficient.

 

[RicModMaker]

Damn. This learning stuff is emptying my wallet. I just found out this thick old 16awg wire isn't man enough. What I thought was good enough actually isnt . I didn't realise that there are 2 lots of amp rating for wire. Chassis amps and power transmission amps. My 22a wire has turned into 3.7a. I'm going to need much thicker gear to guarantee enough amperage.
Mains 2.5mm wire it is then unless someone can give me a better solution?

 

[Maxcat]

Damn. This learning stuff is emptying my wallet. I just found out this thick old 16awg wire isn't man enough. What I thought was good enough actually isnt . I didn't realise that there are 2 lots of amp rating for wire. Chassis amps and power transmission amps. My 22a wire has turned into 3.7a. I'm going to need much thicker gear to guarantee enough amperage.
Mains 2.5mm wire it is then unless someone can give me a better solution?

I'm sure the chassis wiring figure is more relevant for your purpose, another chart here more suited to voltage/distance levels.

http://www.rbeelectronics.com/wtable.htm

 

[RicModMaker]

I'm sure the chassis wiring figure is more relevant for your purpose, another chart here more suited to voltage/distance levels.

http://www.rbeelectronics.com/wtable.htm

I'm trying to make something that won't burn out at sub ohm. So far everything Ive tried is melting or under performing. My mod doesn't hit like a mech and I think its due to the amperage. Of course, I'm probably wrong.
I want to make the next mod bomb proof within reason.

 

[doobedoobedo]

I have about 2 inches of 24AWG in this:

and can quite happily go down to whatever ohms I like - I've had a .2 ohm build on there with no ill effects - nothing getting hot apart from the atty.

The monster uses 14AWG for high current, which is probably a bit of overkill.

For comparison my RC cars which run at around 800W on a full battery use about 6 inches of 10AWG. But the wires can get quite warm.

 

[RicModMaker]

I have about 2 inches of 24AWG in this:

and can quite happily go down to whatever ohms I like - I've had a .2 ohm build on there with no ill effects - nothing getting hot apart from the atty.

The monster uses 14AWG for high current, which is probably a bit of overkill.

For comparison my RC cars which run at around 800W on a full battery use about 6 inches of 10AWG. But the wires can get quite warm.

Looks good. According to the chart you can pull up to about 6a with 14awg.
Do you think the wire may be throttling the power with really low ohms?

 

[doobedoobedo]

For wire the length is as critical as the thickness. (fnaar, fnaar)

Keep the runs short and you're good. the .2 build was drawing 21A/88W through about 2 inches of 24AWG. 3 inches of 14AWG should take 60-80A easily before it gets warm. In short bursts as we do for vaping it should take more than that. And this is multi-core. A solid copper wire would take even more. The charts you see are not reliable, they're for long runs, in your chart the resistance is in ohms per 1000 feet (approx 300M).

In your chart 16 gauge has a resistance of 0.000131758530184 ohms per cm. Negligible. Mains wiring should ba able to take anything you throw at it.

What is melting?

 

[RicModMaker]

For wire the length is as critical as the thickness. (fnaar, fnaar)

Keep the runs short and you're good. the .2 build was drawing 21A/88W through about 2 inches of 24AWG. 3 inches of 14AWG should take 60-80A easily before it gets warm. In short bursts as we do for vaping it should take more than that. And this is multi-core. A solid copper wire would take even more. The charts you see are not reliable, they're for long runs, in your chart the resistance is in ohms per 1000 feet (approx 300M).

In your chart 16 gauge has a resistance of 0.000131758530184 ohms per cm. Negligible. Mains wiring should ba able to take anything you throw at it.

What is melting?

Thanks for that. I didn't take into account the length of the wire.
I've had a few battery holder cables melt but the premade ones have such small wires. Not actually had the bigger wires melt but do feel the power is being throttled compared to a mech. I'll give the mains wire a bash where needed and use thinner where not.
This is really good info you've helped me with and really appreciated.
Small Hammond mod coming soon using 2x14500 in parallel. If it holds up well, I'm going to try serial 18650 with a vv board so want cables that can handle it. With these calculations, I should be able to build something decent so thanks for everything. ;-)